Super-Early Detection of Alzheimer’s Made Possible by Brain Scans

“Tau tangles” and “amyloid plaques” might evoke a Medusa-like image of a head full of chaotic, snake-ridden hair. Unfortunately, these plaques and tangles represent something more real. They’re the hallmarks of Alzheimer’s disease – brain-invading protein formations that used to be detectable only after death.

Within the last decade, however, positron emission tomography, or PET scanning, has made amyloid imaging possible while people are alive. Even more recently, within the past few years, it’s become possible to clearly visualize tau infiltration in the brains of living people who appear normal.

In July, experts on aging gathered in San Francisco for the annual International Association of Gerontology and Geriatrics World Congress. There, they discussed a variety of new frontiers in dementia detection and diagnosis, and what it all means for health providers and everyday people going about their lives.

It might be time to categorize Alzheimer’s in a new way, suggests Dr. Ronald Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center and lead author of a brain-imaging study presented at the conference. A new categorization could provide a more objective, biological basis for scientists working to discover treatments versus relying largely on behavioral symptoms or mental-function tests.

Unlike other research on higher-risk adults who have Alzheimer’s disease in their family history, the Mayo Clinic Study of Aging involves people chosen at random from the general population, Petersen notes. The latest findings come from about 2,800 active participants without dementia, starting in 2004. The study continues to enroll adults from ages 30 to 89, representing six decades of aging.

Tau PET scan comparison

The TAU difference: Brain PET scans from a clinically normal 84-year-old (left) and a 71-year-old with Alzheimer’s dementia. (Courtesy of Mayo Clinic)

In addition to PET scans of the brain, spinal taps from about 850 of the study volunteers provided more data on Alzheimer’s biomarkers, substances that may indicate disease. The researchers measured signs of amyloid and tau proteins in the spinal fluid to correlate with participants’ PET scan images. Magnetic resonance imaging, or MRI scans, were also used along with the PET scans to increase precision.

The study hub of Olmsted County, Minnesota, provides a unique opportunity to follow patients in great depth. Most local residents receive medical care either through Mayo or the Olmsted Medical Center, Petersen notes. “We know more about who lives here than the census takers do,” he says. “We have medical records going back to virtually day one, for many, because they were born and raised in this very stable community.”

To bridge the gap in diversity stemming from the largely white makeup of the local population, the Mayo researchers are embarking on a collaboration with the University of Mississippi Medical Center in Jackson, Mississippi. African-Americans will comprise at least half of study participants, Petersen says.

For experts steeped in the world of dementia, the new findings could be game-changers. However, for an unsuspecting person functioning well and leading a normal life, the implications of having Alzheimer’s protein in the brain are far from certain. Some will go through life without outward signs of the disease and researchers don’t want to cause undue alarm or anxiety.

People participating in the Mayo study are not informed when abnormalities show up on their individual brain scans. “That’s because we don’t know the meaning of it,” Petersen says. “And also, there’s no treatment for it right now. If you’ve got amyloid in the brain, we can’t get rid of it. If an amyloid drug is approved, that’s going to change that whole aspect of it. But, now, we don’t want to burden that 72-year-old woman with, ‘Oh, by the way, you have one of the Alzheimer’s proteins in your brain.’ That’s not fair to her.”

Among the general population, it would be far too expensive and impractical to use PET scans or invasive spinal taps to screen older adults for super-early signs of potential Alzheimer’s disease, Petersen says. Relatively simple blood tests or other biomarkers, not yet available, will be needed to help determine whether people are at low, medium or high risk, he says.

When developed, effective drug treatment for Alzheimer’s likely won’t emerge as a single medication that works for everyone, Petersen says. Instead, therapy will likely involve multiple drug combinations, targeted toward an individual patient’s profile.

Most middle-aged and older U.S. adults will never participate in clinical trials. However, they and their families stand to benefit now from earlier detection of existing dementia, according to another conference offering.

One barrier to timely detection is when primary care providers don’t feel fully confident in their ability to assess early cognitive impairment, presenters said. In addition, family doctors or nurse practitioners may be reluctant to share their concerns with family members and uncertain of which resources to suggest or offer.

To address these needs, the Gerontological Society of America, or GSA, has developed a cognitive impairment toolkit to pull together everything needed to diagnose dementia in one place. This initial process could take as little as five minutes during a routine wellness exam or diabetes checkup.

The downloadable toolkit includes brief tests for clinicians, self-reports for patients and a questionnaire to glean family members’ perceptions. “The family is often more aware of what’s going on than anyone else,” Katie Maslow, an expert on aging and a visiting GSA scholar, said at the conference.

The toolkit also offers nonthreatening approaches for doctors and nurses to open a discussion on brain health and cognitive changes. In addition, clinicians can refer and link patients and families directly to community and caregiver resources and referral sites for whatever help they might need, as soon as possible.

Editor’s Note: This story was written with the support of a journalism fellowship from New America Media, the Gerontological Society of America and the Commonwealth Fund.

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